Emmanuel Joseph Sieyès (3 March 1748 – 20 June 1836), commonly known as Abbé Sieyès, was a French Roman Catholic abbé and clergyman, one of the chief theorists of the French Revolution, French Consulate, and First French Empire. His liberal 1789 pamphlet What is the Third Estate? became the manifesto of the Revolution that helped transform the Estates-General into the National Assembly in June of 1789. In 1799, he was the instigator of the coup d'état of 18 Brumaire (9 November 1799), which brought Napoleon Bonaparte to power. He was also the first to coin the term "sociologie" (French for "sociology") in an unpublished manuscript.